SharePoint 2010 CU update error: CanUpgrade [Microsoft.SharePoint.Administration.SPIisWebSite] failed.

https://social.msdn.microsoft.com/Forums/en-US/f6f30ede-b614-4773-be98-0c9fac29ca37/upgrade-session-failed-100-complete?forum=sharepointadmin

Steps to Resolve:
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Open Central Admin - Manage Web Applications - Select web application - Click on Delete Drop Down (Do not click on Delete Button) - Select Remove SharePoint from IIS Web site - Click following drop down - Remove SharePoint from IIS - Select IIS web site and zone to remove - Check if you see any web site which is not present in IIS - If you see any web site which is not under IIS then just select that and remove it from SharePoint.

Note:- Follow above steps on all SharePoint web servers.

Once above steps are done you can again run the PSConfig upgrade wizard and it should be successfull.

Upgrade command: psconfig.exe -cmd upgrade -inplace b2b -wait -force